1. Field of the Invention
The present invention relates to a liquid raw material supply unit for a vaporizer for supplying a liquid raw material to the vaporizer.
2. Description of Related Art
In recent years, a high-integration design has been demanded for semiconductor memory devices and embedded memory LSIs using capacitors such as DRAM (Dynamic Random Access Memory) and FeRAM (Ferroelectric Random Access Memory). In response to such demands, high dielectric constant materials have to be used for manufacture of semiconductors. The high-dielectric materials are often used in liquid state. In many cases, accordingly, a liquid raw material is supplied to a vaporizer in which the liquid raw material is vaporized, and this vaporized gas is supplied to a reactor. This process therefore needs a liquid raw material supply line for supplying the liquid raw materials to the vaporizer.
If the liquid raw material remains in the liquid raw material line and the vaporizer, it may result in reaction products which will be deposited in the line and the vaporizer. Such deposits are likely to cause various problems; e.g., they become a particle generation source, leading to a lower yield ratio, they clog control valves and line pipes, or they clog nozzles of the vaporizer. To avoid those problems, the liquid raw material supply line is usually subjected to a cleaning process after supply of the liquid raw material to the vaporizer. In the cleaning process, the liquid raw material remaining in the line pipes and the vaporizer is cleaned or washed with a cleaning solution (by liquid-liquid replacement) and then the cleaning solution is removed from the line pipes and the vaporizer by a purge gas (by liquid-gas replacement).
An example of the above liquid raw material supply line is arranged as shown in FIG. 6 that liquid raw material lines 101 and 102 each comprising a valve and pipes for feeding a liquid raw material and a cleaning solution line 103 comprising a valve and pipes for feeding a cleaning solution are connected to a main line 105 with one end connected to a vaporizer and the other end connected to a purge gas line 104. In this liquid raw material line, a liquid raw material is fed from the liquid raw material line 101 or 102 to the main line 105, and the liquid raw material fed into the main line 105 is then supplied to the vaporizer.
For cleaning, here, the cleaning solution is fed from the cleaning solution line 103 to the main line 105, thereby cleaning the line and the vaporizer through which the liquid raw material has passed with the cleaning solution. After cleaning using the cleaning solution, a purge gas is introduced into the purge gas line 104 to thereby remove the remaining cleaning solution from the liquid raw material supply line.
Another example of the liquid raw material supply line is shown in FIG. 7, which is arranged such that monoblock valves X1 to X4 each comprising a plurality of valves are connected to each other through pipes. In this liquid raw material supply unit, a pressurizing gas (e.g., He gas or another inert gas) is fed into a valve V2 of the monoblock valve X1 and then enters a liquid raw material tank 121 through a valve V1 of the monoblock valve X1 and a valve V4 of the monoblock valve X2 to pressurize the liquid raw material to be supplied to the vaporizer through the valve V1 of the monoblock valve X2, and the monoblock valves X3 and X4 in order.
For cleaning, here, when a washing solution is fed into the valve V1 of the monoblock valve X1, the washing solution flows in the monoblock valve X3 via a valve V3 of the monoblock valve X2. The washing solution then flows in a valve V2 of the monoblock valve X3 and a valve V2 of the monoblock valve X4 sequentially. By this process, the passages through which the liquid raw material has passed are cleaned. After cleaning using the washing solution, an inert gas such as an Ar gas is introduced as a purge gas into a valve V3 of the monoblock X1 to remove the remaining washing solution from the passages.
However, both the aforementioned liquid raw material supply lines are fundamentally constructed of a plurality of valves and a plurality of pipes. This construction disadvantageously needs a large mounting space, which could impede miniaturization and high integration.
In the former liquid raw material line, when the cleaning solution is fed into the main line 105 for cleaning, a liquid remaining or staying zone (a dead space) tends to occur in the liquid raw material supply line 101 or 102. When the purge gas is fed into the main line 105, on the other hand, a liquid remaining or staying zone (a dead space) is likely to occur in the liquid raw material supply lines 101 and 102 and the cleaning solution supply line 103 respectively. Thus, a replacement rate (or replacement capability) of the residual or remaining liquid (a liquid-liquid replacement rate and a liquid-gas replacement rate) is poor, which needs much time for replacement of the residual liquid, resulting in a longer cleaning time. This also leads to a prolonged cycle time of a semiconductor manufacturing device and hence a lower manufacturing efficiency. Further, the liquid-gas replacement rate is extremely poor with the result that the cleaning solution remaining after cleaning could not be replaced completely by the purge gas.
In the latter liquid raw material supply line, on the other hand, the time required for cleaning could be shortened (the replacement rate of the residual liquid could be enhanced). However, the monoblock valves X1 to X4 used in the line have very complicated flow passages respectively.